.\" Copyright (c) 2002 Packet Design, LLC. .\" All rights reserved. .\" .\" Subject to the following obligations and disclaimer of warranty, .\" use and redistribution of this software, in source or object code .\" forms, with or without modifications are expressly permitted by .\" Packet Design; provided, however, that: .\" .\" (i) Any and all reproductions of the source or object code .\" must include the copyright notice above and the following .\" disclaimer of warranties; and .\" (ii) No rights are granted, in any manner or form, to use .\" Packet Design trademarks, including the mark "PACKET DESIGN" .\" on advertising, endorsements, or otherwise except as such .\" appears in the above copyright notice or in the software. .\" .\" THIS SOFTWARE IS BEING PROVIDED BY PACKET DESIGN "AS IS", AND .\" TO THE MAXIMUM EXTENT PERMITTED BY LAW, PACKET DESIGN MAKES NO .\" REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING .\" THIS SOFTWARE, INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED .\" WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, .\" OR NON-INFRINGEMENT. PACKET DESIGN DOES NOT WARRANT, GUARANTEE, .\" OR MAKE ANY REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS .\" OF THE USE OF THIS SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, .\" RELIABILITY OR OTHERWISE. IN NO EVENT SHALL PACKET DESIGN BE .\" LIABLE FOR ANY DAMAGES RESULTING FROM OR ARISING OUT OF ANY USE .\" OF THIS SOFTWARE, INCLUDING WITHOUT LIMITATION, ANY DIRECT, .\" INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, PUNITIVE, OR CONSEQUENTIAL .\" DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, LOSS OF .\" USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY THEORY OF .\" LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF .\" THE USE OF THIS SOFTWARE, EVEN IF PACKET DESIGN IS ADVISED OF .\" THE POSSIBILITY OF SUCH DAMAGE. .\" .\" $FreeBSD: src/lib/libc/gen/makecontext.3,v 1.4 2002/12/19 09:40:21 ru Exp $ .\" .Dd September 10, 2002 .Dt MAKECONTEXT 3 .Os .Sh NAME .Nm makecontext , swapcontext .Nd modify and exchange user thread contexts .Sh LIBRARY .Lb libc .Sh SYNOPSIS .In ucontext.h .Ft void .Fo makecontext .Fa "ucontext_t *ucp" .Fa "void \*[lp]*func\*[rp]\*[lp]void\*[rp]" .Fa "int argc" ... .Fc .Ft int .Fn swapcontext "ucontext_t *oucp" "const ucontext_t *ucp" .Sh DESCRIPTION The .Fn makecontext function modifies the user thread context pointed to by .Fa ucp , which must have previously been initialized by a call to .Xr getcontext 3 and had a stack allocated for it. The context is modified so that it will continue execution by invoking .Fn func with the arguments provided. The .Fa argc argument must be equal to the number of additional arguments provided to .Fn makecontext and also equal to the number of arguments to .Fn func , or else the behavior is undefined. .Pp The .Fa "ucp->uc_link" argument must be initialized before calling .Fn makecontext and determines the action to take when .Fn func returns: if equal to .Dv NULL , the process exits; otherwise, .Fn setcontext "ucp->uc_link" is implicitly invoked. .Pp The .Fn swapcontext function saves the current thread context in .Fa "*oucp" and makes .Fa "*ucp" the currently active context. .Sh RETURN VALUES If successful, .Fn swapcontext returns zero; otherwise \-1 is returned and the global variable .Va errno is set appropriately. .Sh ERRORS The .Fn swapcontext function will fail if: .Bl -tag -width Er .It Bq Er ENOMEM There is not enough stack space in .Fa ucp to complete the operation. .El .Sh SEE ALSO .Xr setcontext 3 , .Xr ucontext 3